U.S. American vs Yank

U.S. American

noun

  • A person from the United States of America. 

adj

  • American 

Yank

noun

  • An American: someone from the United States. 

  • A Yankee, a Northerner: someone from the Northern United States, especially from New England. 

How often have the words U.S. American and Yank occurred in a corpus of books? (source: Google Ngram Viewer )